1. Field of the Invention
The present invention relates to an image pickup apparatus including an auto zoom function that controls a zoom lens so that a captured object image constantly has a fixed size.
2. Description of the Related Art
In conventional image pickup apparatuses, an auto zoom function that controls a zoom lens so that a captured object image constantly has a fixed size has been proposed in addition to automatic control of, e.g., an iris, exposure, focus and white balance. Use of the auto zoom function eliminates the need for the troublesome work of consistently adjusting the angle of view by manually performing zooming when one wishes to keep a moving object at a fixed angle of view. However, use of such auto zoom has caused a problem in that once the size of an object relative to a frame (hereinafter referred to as “target angle of view”) maintained by an auto zoom is determined, the target angle of view cannot be changed unless the auto zoom is cancelled.
For example, it is supposed that when a child, which is an object, runs in a footrace in an athletic meet, a user wishes to capture an image of the child at a bust shot angle of view from the start position to the position immediately before the goal and at a full-length portrait angle of view at the goal position at the moment that the child breaks the tape, using an auto zoom. In this case, it is necessary to, first, set the target angle of view so as to be a bust shot angle of view for the start position, and re-set the target angle of view so as to be a full-length portrait angle of view immediately before the goal. However, conventional auto zoom functions do not allow change of a target angle of view during an auto zoom being underway, thus requiring the work of temporarily cancelling the auto zoom immediately before the goal position, re-setting the target angle of view and then restarting the auto zoom.
In response to the aforementioned problem, the image pickup apparatus described in Japanese Patent Application Laid-Open No. H09-149311 includes a manual adjustment zoom button intended to change a target angle of view. Upon the manual adjustment zoom button being operated during an auto zoom being underway, a detection unit detects an input to the manual adjustment zoom button, and automatically temporarily cancels the control of a zoom lens according to the auto zoom, and accepts a manual operation. Consequently, a user can set an object at a desired angle of view using the manual adjustment zoom button. Upon the end of the operation via the manual adjustment zoom button, the size of the object relative to the frame at the point of time when the operation ended is set as a new target angle of view, and an auto zoom is started again. Use of this technique enables easy change of a target angle of view even during an auto zoom being underway.
However, in the conventional art, the zoom speed during the manual operation is not taken into consideration. When a user switches the mode from auto zoom to manual operation, the zoom speed may sharply change unless the user skillfully adjusts the zoom speed of the manual operation to the zoom speed of the auto zoom immediately before the switching to the manual operation, resulting in a problem in that an image giving a feeling of strangeness in appearance may be formed.
For example, when an object is quickly coming toward a user, high-speed zooming is performed to change the angle of view to the wide angle side because of control according to an auto zoom in order to keep the size of the object constant. Here, when the user wishes to change the target angle of view to the wide angle side via a manual operation, it is necessary to perform zooming to the wide angle side at a speed higher than the zoom speed during the auto zoom. However, it is very difficult to estimate the zoom speed of the auto zoom performed immediately before the switching to the manual operation and know the amount of manual input necessary to make a change to achieve a desired target angle of view. Thus, a difference occurs between the zoom speed of the auto zoom performed immediately before the mode switching and the zoom speed of the manual operation, disabling maintenance of the zoom speed continuity, which may cause an image giving a feeling of strangeness in appearance to be formed.
Furthermore, when zooming is performed at a high speed via a manual operation using a zoom lever for changing a zoom speed step by step in accordance with the strength of pressing the zoom lever, which is a manual input unit, the zoom lever can be pressed with a desired strength after passing through the region in which the zoom lever is temporarily pressed with only weak pressing strength, and thus, low-speed zooming is instantaneously performed. In other words, if high-speed zooming is performed by pressing the zoom lever strongly via a manual operation when an object moves largely, also, low-speed zooming is instantaneously performed, thus disabling maintenance of the zoom speed continuity, which may cause a problem similar to the above.